Air streams emitted from various commercial processes, such as cooking with greases and the like in a restaurant, typically contain greases, long chain fats, oils, or other hydrocarbons in the form of vapor or fine dispersions which produce disagreeable smoke and odor when vented directly into the atmosphere. Especially in restaurant cooking operations, these hydrocarbon-laden air streams are normally vented directly into the atmosphere immediately outside of the commercial establishment, the fumes and odors characteristic of these discharged air streams being objectionable and undesirable.
Hydrocarbon-laden air streams from a variety of commercial and industrial processes have long been vented directly into the atmosphere with little or no treatment thereof prior to discharge from the source. However, some attempts have been and are being made to remove the organic materials from these air streams. Filtration of grease-laden air streams has been pursued. However, disposal of the grease-laden filter media presents an additional problem. A process known as "wet-scrubbing" has been suggested and is effective for removal of grease from hydorcarbon-laden air streams but does little to remove odors from the air streams. Further, disposal of grease-laden waste water from this process presents a vexing environmental problem. Incineration of the organic materials in a hydrocarbon-laden air stream has, of course, been accomplished. However, such open-flame processes require tremendous amounts of energy and present inordinately serious fire hazards, especially when used in and around areas where people are present, such as in a restaurant.
The present invention provides a method and apparatus for catalytically oxidizing grease, fats, oils, and/or other hydrocarbons in an air stream emanating from a source, such as from a cooking grill in a restaurant. The invention is particularly useful in those situations where hydrocarbon-laden air streams are emitted from a source at a temperature lower than the nominal operating temperature of a catalyst which is intended to flamelessly oxidize the organic materials in the air stream. The invention renders catalytic oxidative treatment of such hydrocarbon-laden air streams both efficient and economical, especially from the standpoint of energy conservation. In fact, in the operation of the present invention, heat released from the flameless catalytic oxidation of the organic material in the air stream is effectively utilized to at least partially heat the hydrocarbon-laden air stream to the operating temperature of the catalyst prior to passage of the air stream over the catalyst.
The invention generally comprises apparatus which ducts a hydrocarbon-laden air stream at a temperature below the operating temperature of a given catalyst in countercurrent relation or in identically parallel direction, to the relatively hot processed air stream exiting from treatment by the catalyst. As an example, grease and odor-laden air rising from a cooking grill has a temperature substantially less than the 350.degree.-475.degree. F necessary for flameless oxidation by a catalyst such as the well-known and efficient platinum-based catalysts. This relatively low temperature and unprocessed air stream is passed through a heat exchange apparatus prior to passage over the catalyst, the heat exchange apparatus being operatively ducted to the processed and relatively more hot air stream passing from the catalyst. The processed air stream is relatively more hot due at least in part to heat released on flameless oxidation of the hydrocarbons in the air stream on passage over the catalyst. Heat can also be introduced into the unprocessed air stream after passage through the heat exchange apparatus and before passage over the catalyst to bring the unprocessed air stream to a desired temperature. Most of this introduced heat is also present in the processed air stream and is transferred in the heat exchange apparatus to the unprocessed air stream. The present invention both recovers at least some of the heat which is introduced into the unprocessed air stream and provides for generation of additional heat from its own catalytic operation, this recovered and generated heat being utilized to heat a relatively cool unprocessed and organic-laden air stream to a temperature suitable for flameless oxidation by a suitable catalyst. The energy savings thus effected render the invention economical for commercial use. The processed air stream, which is still at a high temperature relative to ambient after passage through the heat exchange apparatus, can be used to heat the building in which the invention is being used or to air condition said building through use of heat absorption refrigeration techniques, or for heating water for use in the commercial process, washrooms, etc. Essentially, the heated processed air stream resulting from the process of the invention can itself be utilized to render the invention even more economical.
The present invention also provides a convenient process for disposing of greases and similar hydrocarbons which typically accumulate in commercial establishments, such as restaurants, which have need for the invention, In essence, this accumulated grease can be used as a "fuel" in the apparatus of the invention, thereby disposing of the waste organics while simultaneously adding heat energy to the processed air stream, which heat energy is utilized to raise the temperature of the unprocessed hydrocarbon-laden air stream as aforesaid. The invention is carried out in these several embodiments at a temperature substantially lower than the flame temperature of the hydrocarbons which are removed from the air stream, the operation of the invention being flameless. Thus, the invention provides a method and apparatus which is significantly more safe in use and which can be utilized in situations where the proximity of combustible materials would present an extreme fire hazard in the presence of open flames.
Accordingly, it is a primary object of the invention to provide a method and apparatus for catalytically oxidizing hydrocarbon-laden air streams which result from commercial and industrial process, such as from a cooking grill in a restaurant.
It is a further object of the invention to provide an economical and energy conserving method and apparatus for efficiently heating relatively low-temperature hydrocarbon-laden air streams to a temperature within the operating range of a catalyst, such heating being accomplished at least in part by heat exchange between the relatively more hot processed air stream exiting from the catalyst.
It is another object of the invention to provide a method and apparatus for flamelessly oxidizing noxious components of cooking or other hydrocarbon-laden air streams essentially to carbon dioxide and water.
It is yet another object of the invention to provide a method for disposal of accumulated greases, oils, and the like from a commercial establishment while simultaneously providing heat energy to a process for catalytically oxidizing hydrocarbon-laden air streams.
It is still another object of the invention to provide a method of utilizing the heat generated by the process for heating the building, air conditioning the building, or heating water for commercial or sanitary use to effectively conserve energy.
Further objects and advantages of the invention will become more apparent in light of the following detailed description of the preferred embodiments of the invention.